Coordinate frames and units

Units

Quantity	Unit
position, length, altitude, radius, SMA	m
velocity and speed	m/s
mass	kg
thrust, impulse	N, N·s
time, UT, period	seconds
/sim schedule offsets and registry times	milliseconds
most angles	degrees
angular rate / acceleration	rad/s, rad/s²
pressure, density, power, energy	Pa, kg/m³, W, J
attitude quaternion	unit x y z w, Body to CCI

Track authoring times are seconds even though live schedule registry times are milliseconds. Camera lengths are meters and camera angles degrees. FX fields state their own unit in the field name or help output.

Working frames

Frame	Meaning	Typical use
ECL	system ecliptic frame	body motion
CCE	celestial-centered ecliptic	body-local inertial data
CCI	celestial-centered inertial about vessel parent	vessel position, velocity, attitude target, burns
CCF / bodyfixed	rotating body frame	ground-relative placement
ENU	east, north, up at a surface point	local ground operations
LVLH	local vertical/local horizontal	orbital-relative guidance
body / assembly	vessel axes and CoM	manual RCS, body-frame impulse

position/cci, velocity/cci, attitude/quat, ctl/burn, teleport state, and default debug impulse all use CCI. CCI has +Z along the parent north pole, +X at the vernal direction, and an equatorial X-Y plane. The attitude quaternion transforms a body-frame vector into CCI.

Use bodies/<parent>/{mu,radius,rotation_rate} for orbital calculations. Surface speed differs from inertial/orbital speed because it includes parent rotation. For camera’s six named placement frames, see Camera.